sqlite Android实现本地缓存

简述：

用到一款聊天框架，需要实现sqlite本地缓存聊天历史，试用sqlite实现本地缓存

步骤：

1. 建立表

public class TableInfo {
public class SingleChatTable {
public static final String TABLENAME= "SingleChatTable";//表名
public static final String FROMJID = "fromJid"; //聊天发送者的Jid
public static final String TOJID = "toJID";//聊天接受者的Jid
public static final String BODY = "body";//如果是聊天室，那么聊天室创建人
public static final String SENDTIME = "sendTime";//发送时间
public static final String IS_READ = "isRead";//是否查看过
/** 表默认的_id*/
public static final String ID ="id";
/**得到创建表的sql语句*/
public  static final String CREATETABLESQL = "CREATE TABLE IF NOT EXISTS "+ TABLENAME +" (" 
        + ID + " INTEGER PRIMARY KEY AUTOINCREMENT," 
+ FROMJID +" TEXT,"
+ TOJID +" TEXT,"
+ BODY +" TEXT,"
+ SENDTIME +" TEXT,"
+ IS_READ +" INTEGER"
+" )";
/**得到删除表的sql语句*/
public static final String DELETETABLESQL = "DROP TABLE IF EXISTS "+ TABLENAME;
}
}

2. 数据库操作类

public class DBHelper extends SQLiteOpenHelper {

private static final String TAG = "DBHelper";

public static final String DB_NAME = "aimp.db";
public static final int DB_VERSION = 1;
public Context mContext;

public DBHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
this.mContext = context;
}


public DBHelper(Context context, String name, CursorFactory factory,
int version) {
super(context, name, factory, version);
}


@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(TableInfo.SingleChatTable.CREATETABLESQL);
}


@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL(TableInfo.SingleChatTable.DELETETABLESQL);
onCreate(db);
}


/**
 * 获取fromJid与toJid之间的聊天记录列表
 * @param fromJid
 * @param toJid
 * @return
 */
public List<SingleChatItem> obtainSingleChatList(String fromJid, String toJid){
List<SingleChatItem> list = new LinkedList<SingleChatItem>();

SQLiteDatabase db = null;
Cursor cursor = null;

try {
db = getReadableDatabase();
// 根据fromJid和toJid获取聊天记录
String selection = "( " + TableInfo.SingleChatTable.FROMJID + "=\""
+ fromJid + "\" and "
+ TableInfo.SingleChatTable.TOJID + "=\""
+ toJid + "\") or (" 
+ TableInfo.SingleChatTable.TOJID + "=\""
+ fromJid + "\" and "
+ TableInfo.SingleChatTable.FROMJID + "=\""
+ toJid + "\")";
// 按照ID获取聊天记录
cursor = db.query(true, TableInfo.SingleChatTable.TABLENAME, null,
selection, null, null, null,
TableInfo.SingleChatTable.ID + " ASC", null);

if (cursor.moveToFirst()) {
do {
SingleChatItem msg = new SingleChatItem();
// 要注意拿数据的顺序，游标不能回头
msg.setFromJid(cursor.getString(cursor
.getColumnIndex(TableInfo.SingleChatTable.FROMJID)));
msg.setToJid(cursor.getString(cursor
.getColumnIndex(TableInfo.SingleChatTable.TOJID)));
msg.setBody(cursor.getString(cursor
.getColumnIndex(TableInfo.SingleChatTable.BODY)));
msg.setSendTime(cursor.getString(cursor
.getColumnIndex(TableInfo.SingleChatTable.SENDTIME)));
list.add(msg);
} while (cursor.moveToNext());
}
Log.i(TAG, "获取单人聊天记录的记录数： " + String.valueOf(list.size()));
} catch (Exception e) {
Log.e(TAG, "获取单人聊天记录失败！ ");
} finally {
if (cursor != null) {
try {
cursor.close();
cursor = null;
} catch (Exception e) {
}
}
if (db != null) {
try {
db.close();
db = null;
} catch (Exception e) {
}
}
}
return list;
}


/**
 * 将单聊类转换为ContentValues
 * @return
 */
private ContentValues getContentValuesByChatItem(SingleChatItem item, boolean isRead){
if (item == null) {
Log.e(TAG, "getContentValuesByChatItem 转换失败，数据为空");
}
ContentValues values = new ContentValues();
// 聊天发送方的JID
values.put(TableInfo.SingleChatTable.FROMJID, item.getFromJid());
// 聊天接受方的JID
values.put(TableInfo.SingleChatTable.TOJID, item.getToJid());
// 发送时间
values.put(TableInfo.SingleChatTable.SENDTIME, item.getSendTime());
// 发送的内容
values.put(TableInfo.SingleChatTable.BODY, item.getBody());
// 是否已读
values.put(TableInfo.SingleChatTable.IS_READ, item.isRead());
return values;
}


/**
 * 插入一条单人聊天聊天记录
 * @param item
 * @param isRead
 * @return
 */
public boolean insertSingleChat(SingleChatItem item, boolean isRead){
boolean result = true;

SQLiteDatabase db = null;
try {
db = getWritableDatabase();
db.beginTransaction();

ContentValues values = getContentValuesByChatItem(item, isRead);
long operating = 0;
operating = db.insert(TableInfo.SingleChatTable.TABLENAME, null,
values);

if (operating < 0) {
result = false;
}
} catch (Exception e) {
result = false;
Log.e(TAG, String.valueOf(e));
} finally {
if (db != null && db.isOpen()) {
db.setTransactionSuccessful();
db.endTransaction();
db.close();
}
}
return result;
}


}

聊天对象

import android.text.TextUtils;

public class SingleChatItem {
private String fromJid;
private String toJid;
private String body;
private String sendTime;
private boolean isRead;
public String getFromJid() {
return fromJid;
}
public void setFromJid(String fromJid) {
if(!TextUtils.isEmpty(fromJid) && fromJid.split("/").length>0)
this.fromJid = fromJid.split("/")[0];
else
this.fromJid = fromJid;
}
public String getToJid() {
return toJid;
}
public void setToJid(String toJid) {
if(!TextUtils.isEmpty(toJid) && toJid.split("/").length > 0)
this.toJid = toJid.split("/")[0];
else
this.toJid = toJid;
}
public String getBody() {
return body;
}
public void setBody(String body) {
this.body = body;
}
public String getSendTime() {
return sendTime;
}
public void setSendTime(String sendTime) {
this.sendTime = sendTime;
}
public boolean isRead() {
return isRead;
}
public void setRead(boolean isRead) {
this.isRead = isRead;
}
}

之后再试用db的时候传入context就可以用了

dbHelper = new DBHelper(this);